Determination of the Optimal Operative Conditions for the Torrefaction of OliveWaste Biomass

The need for new energy sources and the problems associated with waste in the agroforestry industry are an opportunity for the recovery of this waste. For the use of this agricultural waste as energy, di erent pretreatments, such as torrefaction, can be carried out. Torrefaction is a thermochemical treatment involving energetic densification of biomass at temperatures ranging from 200 to 300 C under an inert and anaerobic environment. This study developed a numerical model to evaluate the e ect of temperature and residence time of torrefaction on biomass from olive tree waste to determine optimum operative conditions for the process. Four temperatures and four residence times, in the operation range of the process, were tested to determine the weight loss and the higher heating values (HHVs) of the torrefied sample. From these data, a numerical model was developed to infer the complete behavior of the process in the temperature range between 200 and 300 C and in the residence time range of a few minutes to 2 h. The HHV of the torrefied sample increased at a temperature between 200 and 275 C. However, from 275 to 300 C, there was an HHV decrease. The e ect of the residence time depended on the torrefaction temperature. At low temperatures, there were no statistically significant di erences, although an increase of HHV was detected under 120 min. However, at 250 C this e ect was reversed, and statistically significant di erences were not observed between 30 and 120 min. Overall, the increase of temperature in the torrefaction process reduces the residence time needed to achieve the maximum HHV. As a result, the optimum conditions of torrefaction for this biomass were, approximately, 275 C and 30 min of residence time. This reaction yielded an optimum 5830 cal/g HHV.University of Granada TEP-968 FQM191University of Jaen EIFQM8 FQM17